The overall objective of the proposed research is to reveal physiological mechanisms underlying auditory-vocal interaction in non-human primates. Such mechanisms have fundamental importance to our understanding of human speech production and perception mechanisms but are poorly understood, and there are no adequate non-human primate models available to address these issues at the cellular level. In this application, we will examine our research questions in a highly vocal primate, the common marmoset (Callithrix jacchus). The marmoset provides several important advantages over other non-human primate species: a rich vocal repertoire, a high reproductive rate while in captivity, and a smooth brain allowing easy access to all parts of the cerebral cortex. In the proposed experiments, we will focus on neural substrates of auditory-vocal interactions in marmoset auditory cortex. In Aim 1, we will develop a behavioral paradigm to experimentally induce vocalizations in the common marmoset. The ability to behaviorally (not electrically) elicit vocalizations in monkeys has long been sought by researchers and remains a significant obstacle in the study of vocal control mechanisms in non-human primates. We will study in Aim 2 how various areas of the auditory cortex are involved in auditory-vocal interactions. Findings from this aim will reveal functional and anatomical properties of neurons involved in auditory-vocal interactions in marmoset auditory cortex, and pave the way for future studies of their connectivity with the brain structures involved in vocal production. In Aim 3, we will study the role of behavioral context in auditory-vocal interactions within auditory cortex. Marmosets produce a wide range of vocalizations in different behavioral contexts. We will investigate whether different types of vocalizations produce different modulatory effects in individual auditory cortical neurons. Findings of this research will provide important insight into speech perception mechanisms in humans and establish a non-human primate model to investigate issues related to diseases and dysfunctions in speech and hearing.